Stable Oxygen Isotope Signature of Extant and Extinct Aplodontiids and Evidence for Water Use
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Hillard, Thomas
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Abstract
Aplodontia rufa has a unique kidney anatomy that is inefficient at concentrating
urine, and as a result the water intake for the species is high and its range is limited to
the high precipitation regions of the Pacific coast. This anatomy is often considered to
be a primitive condition for rodents, however we hypothesize it may be a derived
character because of the range of extinct members in the clade. Stable oxygen isotope
measurements from tooth enamel were used to investigate the water usage in the fossil
species Liodontia alexandrae alongside the modern Aplodontia rufa. Previous studies
have shown that animals that are dependent on drinking water and spend more time
around water have a lower stable oxygen isotope ratio in their tooth enamel. So, we
compared the oxygen isotope ratios of the aplodontines to measurements taken from
lagomophs from the same localities that are better at conserving water, including the
modern Sylvilagus bachmani and the extinct Oreolagus wallacei. Our data shows a
significant difference between Aplodontia rufa and Sylvilagus bachmani, but no
difference between Liodontia alexandrae and Oreolagus wallacei. This suggests that
Liodontia does not have the same renal anatomy as A. rufa, and is evidence that the
renal anatomy of A. rufa is a derived trait in the aplodontiine group.
Description
24 pages
Keywords
stable oxygen isotope, water use, aplodontines